Some questions from a newbie!!

i didnt get a root folder so i maked a ROOT folder, and i puted the files where i think it should be, but i didnt find the installer file, so i repplaced it with BOOT.elf but when i starts the SD card menu, its pops-up that if i wanna do it and i click "YES" but then it says: "COULD NOT FIND BOOT.DOL AND BOOT.ELF" what should i do?

You don't need to make a 'root' folder. 'Root' is the beginning of your SD-Card (or any other drive). Example: Let's say you go to "My Computer" on your PC. What you see there is a collection of drives (C:, D:, E:, etc). When you double-click your hard disk (let's say it's named C:) you will start at the base of your hard disk, a.k.a. root.

Now this is the same for any other drives (floppy's, SD cards etc) so by meaning you need to put boot.dol and boot.elf on the root of your SD-Card they simply mean at the base of your card, the start, not put in maps.

The path to your files would be (assuming for now that your SD-Card drive is G:):
G:\boot.elf
G:\boot.dol

And NOT:
G:\MAP1\MAP2\MAP3\boot.dol
G:\MAP1\MAP2\MAP3\boot.elf

The same goes for the other files. Although those that are found in maps can be placed onto the SD-card in that same map (maps like wad/apps) as long as they start out on the root as well.

An sd card would hardly hold any wii games at all. Your best bet would be to get an external hard drive or load from dvd-r's.
Also download and install neogamma from the link in my signature. Its a great program for launching games.